1. Field of the Invention
The present invention generally relates to a one-way clutch to allow the transmission of a rotating torque between inner and outer rings only in one direction and more particularly, to an annular spring for urging engagement members such as sprags disposed between the inner and outer rings in one direction.
2. Description of the Prior Art
FIG. 1A is a side view of a common one-way clutch and FIG. 1B is a cross-sectional view taken along line 1--1 of FIG. 1A. As shown in these figures, the one-way clutch generally has an inner ring 61 and an outer ring 62 (only its inner surface is shown) substantially concentric with the inner ring 61. Between the inner ring 61 and the outer ring 62, a plurality of sprags 63 are disposed spaced from each other at regular intervals to serve as engagement members for engaging the inner ring 61 with the outer ring 62. The sprags 63 are held in place by inner and outer retainers 65, 65 and are each urged in one direction by an annular spring 66 disposed radially between the inner and outer retainers 65. Thus, the one-way clutch transmits a rotating torque from the inner ring 61 to the outer ring 62 only when the inner ring 61 rotates in one direction relative to the outer ring 62.
FIGS. 2-4 are fragmentary plan views of various types of conventional springs for use as the annular spring 66 in the one-way clutch. The spring shown in FIG. 2 is of a basic type which is used when the sprags 63 are disposed at relatively small intervals. As shown in FIG. 2, the spring includes receiving openings 31 having a generally rectangular shape and provided at regular intervals for receiving the respective sprags 63. The receiving openings 31 are defined by transverse sections 33. Each transverse section 33 has a tab 32 projecting from its central portion into the respective receiving opening 31. The tab 32 contacts the sprag 63 placed in the receiving opening 31 in a pressing manner when the spring is assembled in the one-way clutch. Each receiving opening 31 is provided with fillets 31a in its corners. The width w1 of the transverse section 33 is made not larger than that w2 of the tab 32 so that a force applied from the sprag 63 to the tab 32 is well absorbed by elastic torsional deformation of the transverse section 33 connected with the tab 32, that stress is not concentrated on the tab 32 and that the tab 32 is prevented from eventually breaking.
When the distance between adjoining receiving openings 31 (pitch of the receiving openings 31) is required to be too great, an adjusting opening 35 of an elliptic shape is provided between the adjoining receiving openings 31 as shown in FIG. 3 so that the transverse section 33 is provided with a width which is greater than or equal to the width w2 of the tab 32. Accordingly the size of the elliptic adjusting opening 35 increases as the pitch of the receiving openings 31 becomes larger.
However, as the width of the elliptic adjusting opening 35 increases, the transverse section 33 becomes widened at its opposite end portions 33a between a respective corner of the receiving opening 31 and a respective radius of the elliptic adjusting opening 35, resulting in the width of each of the end portions 33a becoming larger than that of the tab 32, as shown in FIG. 4. The end portions 33a wider than the tab 32 being makes it difficult for the transverse section 35 to be torsionally deformed. As a result, stress tends to be concentrated on the tab 32, which will eventually break.